DESCRIPTION: Bacterial biofilms are sessile communities of bacterial cells attached to surfaces and embedded in an extracellular matrix secreted by the attached cells. Biofilms play important roles in contact lens associated eye infections; thus, it is important to understand bacteria-surface interactions and the roles of surface material in these processes. As an important material property, material stiffness is well known to affect the shape, adhesion, proliferation, and migration of eukaryotic cells. However, little is known about the role of materil stiffness in bacterial biofilm formation and associated virulence. This knowledge gap is the motivation of our preliminary study and proposed work outlined in this application. Recently, the investigator's lab demonstrated that the stiffness of poly(dimethylsiloxane) (PDMS) not only affects bacterial adhesion and biofilm growth, but also the size and antibiotic susceptibility of attached cells. By studying Escherichia coli and Pseudomonas aeruginosa biofilm formation on PDMS surfaces with varying Young's modulus (between 0.1 MPa to 2.6 MPa), it was found that material stiffness inversely affects bacterial adhesion and biofilm growth. In addition, the cells n soft surfaces were found longer and more susceptible to antibiotics than those on stiff surfaces. To better understand this newly observed phenomenon, this team will take integrated experimental approaches and computer-based cell tracking to study how material stiffness affects the physiology of bacteria using P. aeruginosa, the leading causative agent of contact lens associated infections, as the model organism. Specifically, the team will investigate the effects of material stiffness on cell motility, cluster formation, expression of virulence factors, and identify the key genes involved in mechanosensing of material stiffness by P. aeruginosa. In addition to the effects on bacterial physiology, the team will also investigate the role of materia stiffness in bacteria-host interactions by studying bacterial killing by ?-defensin-2 and phagocytosis. The results from these studies will provide important missing information about the effects of material properties on bacterial biofilm formation and virulence, and guide the design of smart contact lenses. The long-term goal of this research team is to engineer non-fouling materials to prevent bacterial biofilm formation. In addition to eye infections, such knowledge and technologies are also useful for controlling other infections involving biofilm formation on abiotic surfaces such as those associated with catheters and other implanted biomaterials or medical devices. This project will lead to several important millstones toward this ultimate goal. It has significance in both fundamental understanding of bacteria-surface interactions and the development of novel biomaterials. Thus, this project falls well within NIH's definition of being contributive to improve people's health and save lives.